Various types of rotary drum air classifiers exist which are used in the solid waste separation system. In such arrangements the solid waste is fed onto a conveyor which is located outwardly of an inclined rotating drum and the conveyor extends into the drum. Loose lightweight particles are entrained in the controlled low velocity air stream within the drum which is induced by ar exhaust fan. These systems are arranged to cause the waste particles to separate from each other into heavy and light fractions. Heavy particles are discharged from the conveyor and progress down the inclined drum where they are discharged into a chute at the lower end of the drum. The light fraction is drawn into a plenum. Such a system is available from Iowa Manufacturing Company such as model 8020. In that system the conveyor extends only a short distance into the drum. A disadvantage is that it is necessary to mount the conveyor in a cantilevered fashion. Additionally, the separation technique is not as efficient because of the short distance that the conveyor extends into the drum causing a change in air velocity. This results in some mid-weight particles, rather than a complete division into light and heavy fractions.
Other typical rotary drum classifiers are disclosed in U.S. Pat. Nos. 3,970,547; 4,052,797; 4,070,202; and 4,178,232.